Rear Master Cylinder

[andygrew]

Hi, I have a leaking master cylinder for the rear brake on my '78 500W. I thought it would not be a problem to get a seal kit as Doug lists a kit for a 13mm piston. But when I stripped it down the seals bear no resemblance to those that Doug has in stock. I have also tried Alex Luzzi in Sienna who has sent me pictures of the same kit.

I thought it looked the same as a Brembo but Ducati Paddy says it isn't and his seals won't fit either, even worse he can't supply an alternative unit.

So, has anyone found a supplier for a 13mm Grimeca master cylinder or found a replacement unit that will work?

Thanks Andy

[3potjohn]

From some recent correspondence I had it may be that Brembo PS16 master cylinder can be used however the actuating arm needs modifying or a new arm made to fit.
I rebuilt mine in 2008 and I think it will not be long before I need to do something again.
This link may help
https://www.morini-riders-club.com/foru ... php?t=6743
RGM Norton list a 13mm rebuild kit but I have no idea if it would be suitable

[andygrew]

Thanks for that, I've also found the Gemini Karts replacement master cylinder which looks to be the answer to our prayers! It has all the correct connections and even the bolt holes are correct. The only reservation I have is if the lever end is too big to fit the space available.

Has anyone tried fitting a Gemini cylinder?

[AntietamClassicCycle]

Ariete makes two different kits for 13 mm master cylinders.
https://www.ebay.com/itm/171737291245
https://www.ebay.com/itm/174003968255

[3potjohn]

If you go with the Gemini Karts option do let us know how you get on. It looks promising.

[andygrew]

Thanks for the replies, I don't think either of the Ariete kits look right, I wonder if the cylinder has been changed at some time, although a long time ago, as it seems as if I need the piston with the seals installed as you get for Brembo's. I have now ordered a Gemini cylinder and will let you know if successful. Fingers crossed as I don't what I can do if it doesn't work!

[andygrew]

Good News! the Gemini Karts master cylinder is identical to the original Gremica! I thought the pivot end may be different from the pictures but it turned out to be a rubber gaiter, which is removable.

Only obvious difference is that it is finished in grey rather than black and the operating arm is steel rather than alloy, but again this could be swopped.

So a new cylinder for under £50 is great value, surprisingly it is cheaper to order from Ebay than direct from Gemini Karts, but more importantly will get the 500 back on the road quickly.

Andy

[3potjohn]

That is really good news and I am sure others will be interested in this.

[Michel3007]

Great news indeed. Would you have a link of the master cylinder you bought, Andy? Cheers

[AntietamClassicCycle]

I'm guessing this is it? https://www.geminikarts.co.uk/product/g ... -cylinder/

[Michel3007]

Thank you Charlie, looks like it